Data loggers are electronic devices which automatically monitor and record various ambient parameters, for example temperature and/or humidity, over time. A data logger contains a detector which picks up the information, and one or more electronic circuits for storage, digitization and optionally evaluation of measurement data and for transmission of data to an external data processing device.
Data loggers can perform long-term pick-up of measurement parameters without monitoring personnel being continually present on site. Data loggers are used in field tests, in the monitoring of transports, for example in the monitoring of acceleration values, vibration values and climatic values in truck or rail carriers, for recording of humidity and temperature values in transport and in warehouses, in the pharmaceutical and food industry, for fault analysis of systems, for example for acquisition of voltage fluctuations in or on a system, for monitoring and alerting in production processes and in quality studies, in research, development and training. Data loggers are also used for recording and monitoring of measurement data in the hobby domain, for example in model aircraft.
Measurement data which has been stored and acquired over a longer time interval can be processed, graphically displayed and statistically evaluated for documentation. In addition to measurement data, data loggers often also acquire various predefined events, such as for example a battery change, an operator intervention, or the change of a memory card, which take place on the device during a monitoring interval. Thus such data loggers can satisfy an important criterion of the pharmaceutical, food and chemical industry which is known as the audit trail. The measurement data which have been acquired by the data logger and the data for the audit trail are filed in an internal hardware memory. To evaluate all data, the data logger can be connected by cable to the data processing system, for example a PC, in order to read out the data. The data can also be read out via a cable-based or also a cableless LAN or similar connection. Data loggers are also known which enable data transfer via WiFi technology, Bluetooth or NFC technology to smartphones or tablet computers. After reading out the data, they can be processed with a hardware-specific evaluation software in order to display them in the form of tables or graphics and to prepare documents or reports. These known data loggers have a relatively complex structure and include corresponding cable-linked or wireless interfaces for reading out or for transmitting measurement data.
Known data loggers can be equipped with a screen display which can enable direct display and indication of measurement data and hardware-internal evaluations. Other known data loggers have one or more LEDs with which the system state can be indicated. The LEDs can also be used in some of the known data loggers for indication of the boundary values of one or more monitored parameters being exceeded. Using these data loggers for example the expiration date of a product can also be monitored and displayed by an LED when it has passed.